simple-react-app-kit/packages/lexical/src/plugins/selection-anchor.ts

import type { LexicalEditor } from "lexical"

export interface SelectionAnchor {
  contextElement: HTMLElement
  getBoundingClientRect: () => DOMRect
}

export function runWithEditorFocus(
  editor: LexicalEditor,
  callback: VoidFunction
) {
  const rootElement = editor.getRootElement()
  if (!rootElement) return

  const document = rootElement.ownerDocument
  const selection = document.defaultView?.getSelection()
  const selectionIsInside =
    selection?.focusNode != null && rootElement.contains(selection.focusNode)
  const focusIsInside =
    document.activeElement != null &&
    rootElement.contains(document.activeElement)

  if (selectionIsInside && focusIsInside) {
    callback()
    return
  }

  editor.focus(callback)
}

export function createSelectionAnchor(
  rootElement: HTMLElement
): HTMLElement | SelectionAnchor {
  const document = rootElement.ownerDocument
  const domSelection = document.defaultView?.getSelection()
  const focusNode = domSelection?.focusNode
  let range: Range | null = null

  if (focusNode && rootElement.contains(focusNode)) {
    try {
      range = document.createRange()
      range.setStart(focusNode, domSelection.focusOffset)
      range.collapse(true)
    } catch {
      range = null
    }
  }

  if (!range) return rootElement
  const selectionRange = range

  return {
    contextElement: rootElement,
    getBoundingClientRect: () => {
      const rangeRect =
        typeof selectionRange.getBoundingClientRect === "function"
          ? selectionRange.getBoundingClientRect()
          : null

      if (
        rangeRect &&
        (rangeRect.width > 0 ||
          rangeRect.height > 0 ||
          rangeRect.x !== 0 ||
          rangeRect.y !== 0)
      ) {
        return rangeRect
      }

      const clientRects =
        typeof selectionRange.getClientRects === "function"
          ? Array.from(selectionRange.getClientRects())
          : []

      return clientRects.at(-1) ?? rootElement.getBoundingClientRect()
    },
  }
}